JP3135276B2 - Radiation resistant polypropylene resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polypropylene resin composition which hardly deteriorates in physical properties when irradiated with radiation.

[0002]

2. Description of the Related Art Polypropylene is used for food and medical purposes because it is inexpensive and has a relatively good balance of physical properties. In these applications, sterilization is required, and irradiation is performed for that purpose. Sterilization by radiation is simple, but the molecular weight of the polymer is reduced and the physical properties are reduced.

[0003]

As applications requiring sterilization are increasing, there is a demand for the development of a polypropylene having an excellent balance of physical properties which is relatively unlikely to be deteriorated by irradiation with radiation.

[0004]

Means for Solving the Problems The present inventors have solved the above problems and have intensively searched for polypropylene having excellent radiation resistance and excellent physical property balance, and completed the present invention.

That is, according to the present invention, the intensity of the peak observed at about 20.2 ppm based on tetramethylsilane in ¹³ C-NMR measured with a 1,2,4-trichlorobenzene solution is attributed to a methyl group of a propylene unit. A radiation-resistant polypropylene resin composition comprising a polypropylene having a syndiotactic structure having a sum of peak intensities of 0.5 or more and a thioetherester-based hydroperoxide decomposing agent.

As the polypropylene used in the present invention, a polypropylene having a syndiotactic structure is used. Catalysts used to produce syndiotactic polypropylene include JAEWEN et al., J. Am. Chem.
c., 1988, 110, 6255-6256 can be exemplified, but even with catalysts of different structures, the syndiotactic pentad fraction of polypropylene obtained when propylene homopolymerization is performed is 0.7 Any material that can produce the above polypropylene can be used.

The transition metal compounds having an asymmetric ligand include isopropyl (cyclopentadienyl-1-fluorenyl) hafnium dichloride described in the above literature.
Alternatively, isopropyl (cyclopentadienyl-1-fluorenyl) zirconium dichloride is exemplified.
Examples of the aluminoxane include the following two types of structures 1 and 2 (where R is a hydrocarbon residue having 1 to 3 carbon atoms, n
Is an integer of 1 to 50. ) Are known, and any of them can be used. In particular, methylaluminoxane wherein R is a methyl group and n is 5 or more, preferably 10 or more is used.

[0008]

Embedded image

[0009]

Embedded image The use ratio of the aluminoxane to the transition metal compound is 10 to 100,000,000 times, usually 50 to 5000 times.

The polymerization conditions are not particularly limited, and a solvent polymerization method using an inert medium, a bulk polymerization method substantially free of an inert medium, and a gas phase polymerization method can be used.

Generally, the polymerization is carried out at a temperature of -100 to 200 ° C. and at a pressure of normal pressure to 100 kg / cm ² . Preferably, it is -100 to 100 ° C and normal pressure to 50 kg / cm ² .

The preferred molecular weight is generally about 0.1 to 3.0 dl / g as the intrinsic viscosity measured with a tetralin solution at 135 ° C.

The tacticity of a propylene homopolymer for a syndiotactic pentad fraction ( ¹³ C-
The ratio of the peak intensity attributed to the syndiotactic pentad observed at about 20.2 ppm based on tetramethylsilane in the NMR spectrum to the total sum of the peak intensity attributed to all the methyl groups of propylene. Less than,
The same applies to the above). 0.7
If it is smaller, the properties as crystalline polypropylene are not sufficient and the physical properties are poor, which is not preferable.

Ethylene or α having 4 to 20 carbon atoms
-It is of course possible to use olefins by copolymerization. In this case, the peak observed at about 20.2 ppm based on tetramethylsilane by ¹³ C-NMR measured with a 1,2,4-trichlorobenzene solution Having a highly syndiotactic structure such that the intensity of the peak is 0.5 or more of the sum of the peak intensities attributed to the methyl group of the propylene unit. Here, the ratio of other olefins is 20wt
% Is preferred from the viewpoint of rigidity.

As the thioetherester hydroperoxide decomposing agent used in the present invention, those having various structures are known. Preferred examples include diesters of higher alcohols having about 5 to 25 carbon atoms, such as lauryl alcohol, tridecyl alcohol, palmityl alcohol, and stearyl alcohol. Specifically, dilauryl-3,3'-thiodipropionate, ditridecyl-3,3'-thiodipropionate, dimyristyl-3,3'-thiodipropionate, distearyl-3,3'-thiol Examples include dipropionate.

In the present invention, the ratio of the thioether ester-based hydroperoxide decomposer to polypropylene used is 1 part per 100 parts of polypropylene.
To 0.0001, preferably about 0.5 to 0.001.

In the present invention, trialkylphosphites (isodecyl, tridecyl, etc.), phenyldialkylphosphites (isodecyl, isooctyl, etc.), Fight (isodecyl,
Isooctyl, etc.), triphenyl phosphite, substituted triphenyl phosphite, phospharasic acid (1, 1
-Biphenyl-4,4'-diylbistetrakis (2,
4-bis (1,1′-dimethylethyl) phenyl)) ester, 3,5-di-tert-butyl-4-hydroxybenzylphosphate-diethyl ester, 9,10-dihydro-9-oxa-10-phospho Fopenanthrene-10-
Oxide, sodium bis (4-t-butylphenyl) phosphate, sodium-2,2′-methylene-bis (4,6-di-t-butylphenyl) -phosphate,
1,3-bis (diphenoxyphosphonyloxy) -benzene or an amine-based antioxidant such as alkyl-substituted diphenylamine, diallyl-p-phenylenediamine or a substituted product thereof, 6-ethoxy 2,2 ′, 4
Substituted quinolines such as -trimethyl-1,2-dihydroquinoline, substituted piperidines such as 2,2 ', 6,6'-tetraalkylpiperidine or metal salts of higher carboxylic acids, such as lauric acid, myristic acid, palmitic acid,
Metal salts of acids such as stearic acid such as calcium, zinc and aluminum can be used in combination.

The proportion of these used is about 1 to 0.0001, preferably about 0.5 to 0.001, per 100 parts of polypropylene.

There is no particular limitation on the method of using the composition, and the composition is molded and used by a usual method.

[0020]

The present invention will be further described with reference to examples.

Example 1 Isopropylcyclopentadiene synthesized according to a conventional method
Lithium enyl-1-fluorene is converted to zirconium tetrachloride.
Isopropyl obtained by reacting with
(Lopentadienyl-1-fluorenyl) zirconium dik
0.2 g of Loride and methylaluminoki manufactured by Tosoh Akzo Co., Ltd.
Using 30g of sun (degree of polymerization 16.1), 200 liters of internal volume
Polymerization pressure at 20 ° C with propylene charged in an autoclave
3kg / cm ^Two-G while adding propylene to reach 20
Polymerized for 2 hours, then methanol and acetoacetic acid methyl
And then washed with an aqueous hydrochloric acid solution, and then filtered for 5.
6 kg of syndiotactic polypropylene was obtained.

According to ¹³ C-NMR, this polypropylene had a syndiotactic pentad fraction of 0.935,
The intrinsic viscosity (hereinafter abbreviated as η) measured with a tetralin solution at 1.degree. C. was 1.45 dl / g , and the MW / MN measured with 1,2,4-trichlorobenzene was 2.2.

The polypropylene is granulated by adding 0.1% by weight of calcium stearate and 0.1% by weight of distearyl-3,3'-thiodipropionate to form a 2 mm-thick sheet and irradiating 3 Mrad of γ-ray at 1 Mrad / hr. The following physical properties before and after were measured. Flexural rigidity: kg / cm ² ASTM D-747 (23 ° C) Tensile yield strength: kg / cm ² ASTM D-638 (23 ° C) Elongation at break:% ASTM D-638 (23 ° C) Izod (notched ) Impact strength: kg ・ cm / cm ASTM D-
638 (23 ° C, -10 ° C) Flexural rigidity before irradiation, tensile yield strength, elongation at break, Izod impact strength (23 ° C, -10 ° C) are 6100, 250, respectively.
, 680, 48, and 3.8, and 6100, 255, respectively after irradiation.
, 680, 48 and 3.8, and the physical properties did not change at all after irradiation.

Comparative Example 1 Tris (2,4-di-t-butylphenyl) phosphite was 0.1 wt% as an additive, and dimethyl succinate-1 was added.
-(2-hydroxyethyl) -4-hydroxy-2,
2 ', 6,6'-tetramethylpiperidine polycondensate 0.01
The same procedure as in Example 1 was carried out except that wt% was replaced with 0.1 wt% of calcium stearate and 0.1 wt% of distearyl-3,3′-thiodipropionate, and the flexural rigidity and the tensile yield strength before irradiation were changed. Elongation at break, Izod impact strength
(23 ° C, -10 ° C) are 6200, 260, 550, 45, and 3.
6 after irradiation, 6100, 265, 390, 38, 3.
Was 4.

[0025]

Industrial Applicability The composition of the present invention has excellent radiation resistance and extremely excellent physical property balance, and is extremely valuable industrially.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-60-215036 (JP, A) JP-A-49-39637 (JP, A) JP-A-3-81130 (JP, A) JP-A-2- 274703 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 23/00-23/36 C08K 5/00-5/59

Claims (1)

(57) [Claims] 1. A ¹³ C-NMR measured with a 1,2,4-trichlorobenzene solution, based on tetramethylsilane,
Radiation resistance consisting of syndiotactic polypropylene and thioetherester hydroperoxide decomposers whose peak intensity observed at 20.2 ppm is 0.5 or more of the sum of the peak intensity attributed to the methyl group of the propylene unit Polypropylene resin composition.